ESP-NOW netdev interface

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WiFi based ESP-NOW network device driver

Related CPUs

ESP CommonCommon modules for Espressif ESP SoCs

ESP32 SoC SeriesImplementation for Espressif ESP32 SoC Series

ESP8266 / ESP8285RIOT-OS port for Espressif's ESP8266 / ESP8285 MCUs

This module realizes a netdev interface using Espressif’s ESP-NOW technology which uses the built-in WiFi module.

With ESP-NOW, the ESP nodes (ESP32 and ESP8266) provide a connectionless communication technology, featuring short packet transmission. It applies the IEEE802.11 Action Vendor frame technology, along with the IE function developed by Espressif, and CCMP encryption technology, realizing a secure, connectionless communication solution.

The RIOT port for ESP implements in module esp_now a netdev driver which uses ESP-NOW to provide a link layer interface to a meshed network of ESP nodes. In this network, each node can send short packets with up to 250 data bytes to all other nodes that are visible in its range.

Note

Due to symbol conflicts in the esp_idf_wpa_supplicant_crypto module used by the esp_now with RIOT’s crypto and hashes modules, ESP-NOW cannot be used for application that use these modules. Therefore, the module esp_now is not enabled automatically if the netdev_default module is used. Instead, the application has to add the esp_now module in its makefile when needed.

USEMODULE += esp_now

For ESP-NOW, ESP nodes are used in WiFi SoftAP + Station mode to advertise their SSID and become visible to other ESP nodes. The SSID of an ESP node is the concatenation of the prefix RIOT_ESP_ with the MAC address of its SoftAP WiFi interface. The driver periodically scans all visible ESP nodes.

The following parameters are defined for ESP-NOW nodes.

Parameter	Default	Description
ESP_NOW_SCAN_PERIOD_MS	10000UL	Defines the period in ms at which an node scans for other nodes in its range. The default period is 10 s.
ESP_NOW_SOFT_AP_PASS	“ThisistheRIOTporttoESP”	Defines the passphrase as clear text (max. 64 chars) that is used for the SoftAP interface of ESP-NOW nodes. It has to be same for all nodes in one network.
ESP_NOW_CHANNEL	6	Defines the channel that is used as the broadcast medium by all nodes together.
ESP_NOW_KEY	NULL	Defines a key that is used for encrypted communication between nodes. If it is NULL, encryption is disabled. The key has to be of type uint8_t[16] and has to be exactly 16 bytes long.

Note

The ESP-NOW network interface (module esp_now) and the Wifi network interface (module esp_wifi) can be used simultaneously, for example, to realize a border router for a mesh network which uses ESP-NOW. In this case the ESP-NOW interface must use the same channel as the AP of the infrastructure WiFi network. All ESP-NOW nodes must therefore be compiled with the channel of the AP asvalue for the parameter ‘ESP_NOW_CHANNEL’.

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Author: Gunar Schorcht